It would be great, if your application could create interaction flow maps for user's projects. Firstly, it is very useful, when designing communicates with developers. Secondly, it is helpful, because when you create the prototype, you can see where (on which page) you can create something more convenient. Moreover, if you watch at the map, you would see all your mistakes.
So, I think, the map is indispensable thing during a prototyping. And I will look forward to this update.

For now when you create an android mock there is no way to set tablet size like 1280x800. You can set working area size, but preview will show phone (with initial phone size) anyway.
iPad mock has only iOS specific items

It should be possible to add the assets from outside (upload) from users exisitng element libraries, and not only create them in the app as described, for many it could save time building the own asset library:)

Let's consider this typical case:
I draw a slide A, with a button linking to slide Z (a sort of fake "popup page"). Then slide Z has a link to go back to slide A.
Now I design another slide B with a button linking to slide Z, but I cannot use it as intended because when I click on Z, I go back to A!

Current solution is to duplicate Z -> Z1 and then link B to Z1, having care to change the link in Z1 (now it should link to B).

I think the ideal solution would be you provide a special new widget, "a back button" (whose internal link is "... back()") we could insert in our slides

Let's consider this typical case:
I draw a slide A, with a button linking to slide Z (a sort of fake "popup page"). Then slide Z has a link to go back to slide A.
Now I design another slide B with a button linking to slide Z, but I cannot use it as intended because when I click on Z, I go back to A!

Current solution is to duplicate Z -> Z1 and then link B to Z1, having care to change the link in Z1 (now it should link to B).

Just wanted to share a tip with you – it’s quite easy to create a popup dialog using a master page.
1. Let’s say you have a page where you want to show a dialog.
2. Create a new page, draw the dialog which you need.
3. Now, set the Master page to point to a page in step 1.

Would be nice to be able to link screens together via the native android back button. At the moment in preview mode I can follow links between pages that I create, but I can't return to a previous page via back button like on native Android phones. Being able to switch between pages in the pages menu down the button of the ui is great, but being more like the actual device would be ideal.

Basically, you can convert any element into a scroll container by right clicking → Grouping → Scroll container.

The your element will be converted into a special container which supports scrolling in the preview.
When you select the element, you can edit both visible area and scrollable area using special handles.